Hot melt adhesives are solid at room temperature while generally being applied in the molten or liquid state. Typically, these adhesives are provided in the form of blocks and because of their tacky nature, the solid adhesive blocks not only stick to each other or adhere to mechanical handling devices, but also pick up dirt and other contaminants during transport. Additionally, certain applications that require high tack formulations result in blocks that will deform or cold flow unless supported during shipment.
Various methods of packaging hot melt adhesives have been developed to address the above concerns. In one method, non-tacky powders are applied onto the hot melt adhesives, and the contents are bagged in packaging films. In some applications, the packaging films must be removed before melting the hot melt adhesives. In other methods, and as taught in U.S. Pat. No. 5,373,682 and U.S. Pat. No. 7,350,644, the packaging film is a part of the hot melt adhesive, and the packaging film is dissolved with the adhesive during the melting stage. While these films may not deleteriously affect the adhesive properties, for they are in minor quantities (typically less than 5 wt % of the total weight), the films may not readily blend into the molten hot melt adhesives during the heating and application stage. The immiscible portion of the packaging film separates from the hot melt adhesive as a distinct and separate layer by floating on the surface of the melt and/or adhering to the walls of the melt tank, and over time, can cause mechanical problems for the adhesive melt tanks. Because there are numerous types of hot melt adhesives based on various chemistries, the packaging films must be selected to ensure good miscibility with the chosen hot melt adhesive.
There continues to be a need in the art for hot melt adhesive packaging films that allows for wider applicability of hot melt adhesives. The current invention fulfills this need.